The Electric Field Instrument (EFI) for THEMIS

Bonnell, J. W.; Mozer, F. S.; Delory, G. T.; Hull, A. J.; Ergun, R.; Cully, C. M.; Angelopoulos, V.; Harvey, P.

doi:10.1007/s11214-008-9469-2

Cited by 440 publications

(489 citation statements)

References 17 publications

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“…The ADP has an additional constraint, the moment of inertia (MOI) that it imparts on the spacecraft. The MOI constraint has been the primary limiting factor in axial boom length on a number of previous missions (Pankow et al 2001;Ergun et al 2001;Bonnell et al 2008). Shorter axial booms are one of the principal reasons that DC electric fields are less accurate in the axial component.…”

Section: Science Requirementsmentioning

confidence: 99%

The Axial Double Probe and Fields Signal Processing for the MMS Mission

et al. 2014

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The Axial Double Probe (ADP) instrument measures the DC to ∼ 100 kHz electric field along the spin axis of the Magnetospheric Multiscale (MMS) spacecraft (Burch et al., Space Sci. Rev., 2014, this issue), completing the vector electric field when combined with the spin plane double probes (SDP) (Torbert et al., Space Sci. Rev., 2014, this issue, Lindqvist et al., Space Sci. Rev., 2014. Two cylindrical sensors are separated by over 30 m tip-to-tip, the longest baseline on an axial DC electric field ever attempted in space. The ADP on each of the spacecraft consists of two identical, 12.67 m graphite coilable booms with second, smaller 2.25 m booms mounted on their ends. A significant effort was carried out to assure that the potential field of the MMS spacecraft acts equally on the two sensors and that photo-and secondary electron currents do not vary over the spacecraft spin. The ADP on MMS is expected to measure DC electric field with a precision of ∼ 1 mV/m, a resolution of ∼ 25 µV/m, and a range of ∼ ±1 V/m in most of the plasma environments MMS will encounter. The Digital Signal Processing (DSP) units on the MMS spacecraft are designed to perform analog conditioning, analog-to-digital (A/D) conversion, and digital processing on the ADP, SDP, and search coil magnetometer (SCM) (Le Contel et al., Space Sci. Rev., 2014, this issue) signals. The DSP units include digital filters, spectral processing, a high-speed burst memory, a solitary structure detector, and data compression. The DSP uses precision analog processing with, in most cases, > 100 dB in dynamic range, better that −80 dB common mode rejection in electric field (E) signal processing, and better that −80 dB cross talk between the E and SCM (B) signals. The A/D conversion is at 16 bits with ∼ 1/4 LSB accuracy and ∼ 1 LSB noise. The digital signal processing is powerful and highly flexible allowing for maximum scientific return under a limited telemetry volume. The ADP and DSP are described in this article.

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Section: Science Requirementsmentioning

confidence: 99%

The Axial Double Probe and Fields Signal Processing for the MMS Mission

et al. 2014

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“…At this time, ARTEMIS P1 sat just upstream from the Moon, in the undisturbed solar wind. We show a selection of the observations made by the electrostatic analyzer (ESA) [McFadden et al, 2008], fluxgate magnetometer (FGM) [Auster et al, 2008], electric field instrument (EFI) [Bonnell et al, 2008], and search-coil magnetometer (SCM) [Roux et al, 2008] instruments in Figure 1.…”

Section: High-altitude Observationsmentioning

confidence: 99%

Evidence for small‐scale collisionless shocks at the Moon from ARTEMIS

Halekas

Poppe

McFadden

et al. 2014

Geophysical Research Letters

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ARTEMIS observes structures near the Moon that display many properties commonly associated with collisionless shocks, including a discontinuity with downstream compression of magnetic field and density, heating and wave activity, and velocity deflections away from the Moon. The two-probe ARTEMIS measurements show that these features do not exist in the pristine solar wind and thus must result from lunar influences. Discontinuity analyses indicate mass flux and heating across the boundary, with the normal velocity dropping from supermagnetosonic to submagnetosonic across the discontinuity. The shock location with respect to crustal magnetic fields suggests a causal relationship, implying that solar wind protons reflected from crustal fields may produce the observed structures. These observations may indicate some of the smallest shocks in the solar system (in terms of plasma scales), driven by solar wind interaction with magnetic fields on the order of the ion gyroradius and inertial length.

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“…The main goal of this mission is to conduct multi-point investigations of substorm phenomena in the tail of the terrestrial magnetosphere (Sibeck and Angelopoulos, 2008). For the current study, Search Coil Magnetometer (SCM) observations (Le Contel et al, 2008) and plasma measurements of the Electric Field Instrument (EFI) (Bonnell et al, 2008) were analyzed. The three search coil antennas cover the same bandwidth, from 0.1 Hz to 4 kHz, in the ULF/ELF frequency range.…”

Section: Data Description and Processing Techniquementioning

confidence: 99%

Observations and modeling of forward and reflected chorus waves captured by THEMIS

et al. 2011

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Abstract. Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms) spacecraft Search Coil Magnetometer (SCM) and Electric Field Instrument (EFI) at ELF/VLF frequencies up to 4 kHz at L ≥ 8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar, discrete structure and rising tones, reflected waves are attenuated by a factor of 10-30 and have 10% higher frequency than concurrently-observed forward waves. Modeling of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger.

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The Electric Field Instrument (EFI) for THEMIS

Cited by 440 publications

References 17 publications

The Axial Double Probe and Fields Signal Processing for the MMS Mission

The Axial Double Probe and Fields Signal Processing for the MMS Mission

Evidence for small‐scale collisionless shocks at the Moon from ARTEMIS

Observations and modeling of forward and reflected chorus waves captured by THEMIS

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